>> Narrator: FROM THE VERY EDGE
OF OUR SOLAR SYSTEM, A COMET
SPEEDS TOWARD EARTH.
IT CUTS THROUGH THE ATMOSPHERE AND PLUNGES INTO THE
PACIFIC OCEAN NEAR
SAN FRANCISCO, CREATING A BLAST
MORE POWERFUL THAN ANY THERMONUCLEAR WEAPON.
>> ANYONE WHO'S OUTSIDE WOULD
ESSENTIALLY BE VAPORIZED,
ALMOST. >> Narrator: IT CAUSES A
MEGA TSUNAMI THAT DEVASTATES THE
WEST COAST.
>> MOST OF THE CITIES ALONG THE OCEAN WOULD BE WIPED OUT.
>> Narrator: FOR BILLIONS OF
YEARS, COMETS HAVE STRUCK EARTH
COUNTLESS TIMES, CAUSING UNTOLD DESTRUCTION, AND IT COULD HAPPEN
AGAIN.
>> IF IT'S A LARGE COMET,
FRANKLY, I'M NOT SURE WE<i> COULD</i> DO ANYTHING ABOUT IT. --<font color="#FFFF00"> Captions by VITAC --</font><font color="#00FFFF">
www.vitac.com</font> CAPTIONS PROVIDED BY
CREATIVE DIFFERENCES >> Narrator: "COMET CATASTROPHE"
ON "MEGA DISASTERS."
OVER THE AGES, COMETS HAVE BEEN
SEEN AS BAD OMENS. PEOPLE BELIEVED ONE COMET
PORTENDED THE ASSASSINATION OF
JULIUS CAESAR AND ANOTHER THE
BLACK DEATH IN MEDIEVAL ENGLAND. >> DURING THE MIDDLE AGES,
COMETS WERE THOUGHT OF AS
WARNING SIGNS -- MISSILES SHOT
AT A SINFUL EARTH FROM THE RIGHT HAND OF AN AVENGING GOD. >> Narrator: SOME CULTURES
DEPICTED THEM AS BLAZING SWORDS,
SLASHING THE NOCTURNAL SKY AS AN
EXPRESSION OF DIVINE WRATH. BUT BY THE 17th CENTURY,
ASTRONOMERS WERE BEGINNING TO
UNDERSTAND THE TRUE NATURE OF
COMETS AS PHYSICAL OBJECTS, RATHER THAN SUPERNATURAL
CREATURES OR APPARITIONS.
USING ISAAC NEWTON'S TECHNIQUES,
BRITISH ASTRONOMER EDMOND HALLEY CALCULATED THE ORBITS OF 24
COMETS.
>> HALLEY WAS THE FIRST TO NOTE,
ALONG WITH HIS COLLEAGUE NEWTON, THAT COMETS ARE CELESTIAL
OBJECTS.
THEY'RE IN ORBIT AROUND THE SUN
JUST LIKE THE PLANETS, EXCEPT THEY'RE ON VERY ELONGATED
ORBITS, SO THEY CAN CROSS THE
EARTH'S ORBIT ONCE ON THE WAY IN
AND ONCE ON THE WAY OUT. >> Narrator: HALLEY BOLDLY
ANNOUNCED THAT THREE OF THEM --
THE ONES SEEN IN 1531, 1607, AND
1682 -- WERE THE SAME COMET ON ITS PERIODIC VISITS TO EARTH.
HE PREDICTED THAT THE COMET
WOULD RETURN EVERY 76 YEARS, AND
HE WAS RIGHT. HALLEY'S COMET DID RETURN IN
1758, AS IT HAS DONE ROUGHLY
EVERY 76 YEARS SINCE.
HALLEY'S DISCOVERY CHANGED THE STATUS OF COMETS FROM MYSTICAL
OMEN TO REAL AND PHYSICAL
THREAT.
>> THE FEAR OF COMETS WAS SORT OF TRANSFERRED FROM A SIGN OF AN
IMPENDING DISASTER -- SOME SORT
OF AN APPARITION -- TO OBJECTS
THAT ACTUALLY COULD HIT THE EARTH, SO WE WENT FROM WARNING
SHOTS TO ACTUAL MISSILES.
>> Narrator: ONE OF THOSE
MISSILES MIGHT HAVE CHANGED THE WORLD 4,800 YEARS AGO, AND
EXPERTS THINK THAT ANOTHER
DEADLY MISSILE COULD STRIKE
EARTH WITH VERY LITTLE WARNING. SINCE ITS BIRTH 4.6 BILLION
YEARS AGO, EARTH HAS BEEN
PUMMELED BY THOUSANDS OF COMETS
AND ASTEROIDS. SCIENTISTS THINK THAT SUCH
IMPACTS MAY HAVE CAUSED TWO OR
MORE OF FIVE GLOBAL EXTINCTIONS.
THE LATEST ONE, 65 MILLION YEARS AGO, IS THOUGHT TO HAVE KILLED
MORE THAN 75% OF THE LIVING
ORGANISMS ON EARTH, INCLUDING
THE DINOSAURS. [ DINOSAURS WAILING ]
THESE MAJOR COSMIC STRIKES SEEM
TO OCCUR AT VERY LONG INTERVALS. >> THE TIME BETWEEN IMPACTS
DEPENDS VERY MUCH UPON THE SIZE
OF THE OBJECT IMPACTING. FOR EXAMPLE, AN OBJECT A
KILOMETER IN DIAMETER MAY HIT
ONCE EVERY 10 MILLION YEARS,
WHEREAS OBJECTS 10 METERS IN DIAMETER MIGHT HIT THE EARTH A
COUPLE OF TIMES A WEEK.
>> Narrator: BUT A FEW
SCIENTISTS NOW SUGGEST THAT, DURING THE LAST 10,000 YEARS,
THE SO-CALLED HOLOCENE EPOCH,
EARTH MAY HAVE SUFFERED A SERIES
OF MORE FREQUENT, LARGE, CATASTROPHIC IMPACTS.
THEY ARGUE THAT, IF A NUMBER OF
NEWLY RESEARCHED GEOLOGICAL
STRUCTURES CAN BE CONFIRMED TO BE COMET-IMPACT CRATERS, IT
WOULD INDICATE THAT COMETS HAVE
STRUCK EARTH MORE FREQUENTLY
THAN PREVIOUSLY THOUGHT AND THAT WE MAY BE DUE FOR ANOTHER
DEVASTATING IMPACT. >> IF WE ARE ABLE TO PROVE THAT
WE HAVE THIS MANY CRATERS WITHIN
THE HOLOCENE, IT IMPLIES THAT
THERE SHOULD BE A LARGE IMPACT ON THE AVERAGE OF ABOUT EVERY
1,000 TO 3,000 YEARS, AND SO WE
SHOULD HAVE ANOTHER IMPACT
WITHIN ABOUT 1,000 YEARS. >> Narrator: BUT TO DATE,
SCIENTISTS HAVE FOUND ONLY ABOUT
170 IMPACT CRATERS ON EARTH, OF
WHICH ONLY 2 WERE CAUSED BY SUBSTANTIAL STRIKES WITHIN THE
LAST 2.6 MILLION YEARS.
FINDING MORE LARGE-IMPACT
CRATERS MAY INDICATE THAT A MAJOR COMET STRIKE WITHIN THE
NEXT MILLENNIUM IS POSSIBLE.
DR. BRUCE MASSE AND HIS
COLLEAGUES THINK THAT RECENT LARGE CRATERS MIGHT BE FOUND IN
THE OCEANS.
>> CURRENTLY, THERE'S OVER 170
KNOWN IMPACTS THAT HAVE BEEN ABSOLUTELY VALIDATED BY PHYSICAL
METHODS.
OF THOSE IMPACTS THAT HAVE BEEN
DOCUMENTED, THERE ARE NONE IN THE OCEANS.
AND YET THE OCEANS COVER MORE
THAN 70% OF THE EARTH'S
LANDMASS. SO WE ARE MISSING A LARGE
PERCENTAGE OF RECENT IMPACTS
BECAUSE THEY OCCURRED IN THE
OCEAN. >> Narrator: ACCORDING TO
DR. ABBOTT AND DR. MASSE, ONE OF
THOSE MISSING IMPACTS MAY HAVE
HAPPENED 4,800 YEARS AGO. THEY BELIEVE THAT ITS
CATASTROPHIC EFFECTS COULD HAVE
INSPIRED THE STORIES OF THE
GREAT FLOOD DESCRIBED IN THE BIBLE AND OTHER ACCOUNTS.
THROUGHOUT THE ANCIENT WORLD,
DIFFERENT CULTURES FROM ASIA AND
EUROPE TO THE AMERICAS HAD LEGENDS OF A GREAT FLOOD.
>> BECAUSE WE ONLY HAVE TRULY
ONE UNIVERSAL MYTH, THAT'S THE
MYTH OF THE GREAT FLOOD, IT WAS MY HYPOTHESIS THAT PERHAPS IT
WAS EVIDENCE OF A GLOBALLY
CATASTROPHIC EVENT. >> Narrator: ACCORDING TO
DR. MASSE, THIS GLOBALLY
CATASTROPHIC EVENT MAY HAVE BEEN
THE IMPACT OF A COMET CRASHING INTO EARTH. MANY OF THE LEGENDS DESCRIBE
SUPERNATURAL CREATURES OR FIERY
OBJECTS APPEARING IN THE SKY
AROUND THE TIME OF THE FLOOD. >> SOMETIMES THESE THINGS ARE
DESCRIBED EXACTLY LIKE COMETS,
AS FLAMES IN THE SKY.
BUT AT LEAST 33 OF THESE MYTHS TALKED ABOUT CREATURES THAT WERE
SUGGESTIVE OF A COMET.
>> Narrator: DR. MASSE SEES
FURTHER EVIDENCE OF WIDESPREAD DISASTER IN A SERIES OF GLOBAL
CHANGES THAT OCCURRED 4,800
YEARS AGO.
AT THAT TIME, ADVANCED SOCIETIES WERE ALREADY DEVELOPING IN MANY
PARTS OF THE WORLD.
>> THIS WAS ALREADY THE TIME OF
THE FIRST DYNASTY OF PHARAOHS LIVING IN EGYPT -- VERY ADVANCED
CIVILIZATION.
>> Narrator: THEN, AROUND THE
YEAR 2800 B.C.E., THERE WAS A SERIES OF SUDDEN CLIMATE AND
SOCIAL CHANGES ACROSS THE GLOBE.
>> ALL OF A SUDDEN, WE GET A
COOLER ENVIRONMENT. AREAS THAT HAD BEFORE BEEN
FORESTS, ALL OF A SUDDEN ARE
SAVANNAS.
THEY'RE OPEN GRASSLANDS. >> Narrator: THE RELATIONSHIP
BETWEEN THE OCEANS AND THE
ATMOSPHERE ALSO CHANGED.
>> THE WELL-KNOWN EL NIÑO SOUTHERN OSCILLATION -- IT'S
REALLY A DRIVER FOR CLIMATE ON
THE EARTH -- UNDERGOES A
PROFOUND CHANGE ITSELF ABOUT 4,800 YEARS AGO IN TERMS OF ITS
PERIODICITY, IN TERMS OF ITS
INTENSITY.
>> Narrator: ALSO DURING THIS TIME, THERE WERE A NUMBER OF
HUMAN MIGRATIONS.
>> POPULATIONS ARE MOVING
AROUND, LANGUAGE DISPERSALS, FOR EXAMPLE.
WE GOT AUSTRONESIANS MOVING OUT
OF TAIWAN AND MAINLAND CHINA
DOWN TO SOUTHEAST ASIA. WE GET INDO-ARYANS MOVING OUT OF
NORTHERN INDIA INTO EASTERN AND
CENTRAL EUROPE.
>> Narrator: DR. MASSE SUGGESTS THAT ALL THESE SOCIAL UPHEAVALS
AND CLIMATIC CHANGES CAN BE
TRACED TO A GREAT FLOOD THAT HE
BELIEVES WAS CAUSED BY A COMET STRIKE.
>> WE'RE SEEING MULTIPLE
DIFFERENT THINGS THAT SUGGEST TO
US WE'RE LOOKING AT A SINGLE EVENT AT 4,800 YEARS AGO AS A
CAUSAL EXPLANATION FOR ALL OF
THESE MYTHS, AND IT SEEMS TO BE
AN OCEANIC-COMET IMPACT. >> Narrator: IN THE COURSE OF
HIS RESEARCH, DR. MASSE
DISCOVERED THAT THE GEOGRAPHICAL
DISTRIBUTION OF CERTAIN MYTH MOTIFS SEEMED TO BE CENTERED ON
A SPECIFIC LOCATION.
>> I ANALYZED 175 GREAT-FLOOD
MYTHS WORLDWIDE. AND IF YOU MAP THESE OUT, THE
DISTRIBUTION OF THESE MYTHS,
THEY ACTUALLY SORT OF MAKE A
BROAD CIRCLE APPROXIMATELY ABOUT 9,000 KILOMETERS AWAY FROM A
CENTRAL PART IN THE
INDIAN OCEAN. AND IT WOULD APPEAR THAT THIS IS
TELLING US THAT THERE WAS A
COMET IMPACT AT THAT LOCATION.
LOOKING AT THE ENVIRONMENTAL INFORMATION CONTAINED IN THOSE
MYTHS, SUCH THINGS AS THE AMOUNT
OF RAINFALL OR THE PRESENCE OF
HURRICANE-FORCE WINDS, TSUNAMIS, ALL OF THESE MYTHS TOGETHER
FORMED A LOGICAL PICTURE OF
SOMETHING HAPPENING AT A SINGLE
POINT IN TIME. >> Narrator: IT IS DIFFICULT TO
ASSIGN AN EXACT DATE TO THE
GREAT FLOOD, BUT DR. MASSE
SUGGESTS THAT THE LEGENDS THEMSELVES MAY POINT SCIENCE IN
THE RIGHT DIRECTION.
>> I WAS ABLE TO HYPOTHESIZE A
PRECISE DATE FOR THIS EVENT BY LOOKING AT WHAT WAS IN THE
MYTHS, TALKING ABOUT
CONJUNCTIONS OF PLANETS AND
CERTAIN CONSTELLATIONS, LUNAR ECLIPSES, SOLAR ECLIPSE, AND
CONJUNCTION OF FOUR OR FIVE
NAKED-EYE-VISIBLE PLANETS AT A
SINGLE POINT IN TIME IS A VERY RARE EVENT.
AND USING THE SOFTWARE ASTRONOMY
PROGRAMS, I WAS ABLE TO COME UP
WITH A SERIES OF EVENTS THAT OCCURRED IN 2807 B.C.
>> Narrator: DR. MASSE THEORIZES
THAT A MASSIVE COMET, PERHAPS
THREE-MILES WIDE, MAY HAVE CRASHED INTO THE INDIAN OCEAN
930 MILES SOUTHEAST OF
MADAGASCAR.
ACCORDING TO IMPACT MODELS CALCULATED WITH DATA COMPILED BY
DR. ABBOTT...
THE COMET WOULD HAVE HIT THE
WAVES AT MORE THAN 100,000 MILES PER HOUR WITH OVER 30 MILLION
MEGATONS OF ENERGY, GENERATING A
MEGA TSUNAMI THAT WOULD HAVE
DEVASTATED COASTAL LANDS AND HUMAN SETTLEMENTS ON FOUR
CONTINENTS.
OVER MOST OF THE WORLD,
TORRENTIAL RAINS, CREATED BY THE VAST INJECTION OF SEAWATER AND
IMPACT DEBRIS INTO THE UPPER
ATMOSPHERE, WOULD HAVE FLOODED
THE LANDS. SMALL AEROSOL IMPACT PARTICLES
WOULD HAVE BEEN EJECTED INTO THE
STRATOSPHERE, BLOCKING THE SUN'S
RADIATION...AND GENERATING COOLER TEMPERATURES ACROSS THE
GLOBE.
>> BASED ON THE MYTHOLOGY AND
BASED ON THE ARCHEOLOGICAL RECORD THAT WE SEE, I WOULD
SUGGEST THAT PERHAPS 50% OF ALL
PEOPLE DIED, EITHER DIRECTLY AS
A CONSEQUENCE OF THE IMPACT AND IMPACT-RELATED EVENTS OR FROM
STARVATION IN THE MONTHS THAT
FOLLOWED.
>> Narrator: BUT MYTHOLOGICAL ACCOUNTS ARE NOT PROOF.
>> MYTHOLOGY BY ITSELF CANNOT
REALLY PROVE ANYTHING WHEN IT
COMES TO LOOKING AT NATURAL EVENTS.
WE NEED PHYSICAL EVIDENCE
ITSELF.
>> Narrator: SCIENTISTS ARE SEARCHING FOR THAT PHYSICAL
EVIDENCE IN THE INDIAN OCEAN.
THERE, PROOF OF A COLOSSAL COMET
STRIKE MAY LIE HIDDEN IN ROCKS SMALLER THAN A HUMAN HAIR. >> Narrator: SOME SCIENTISTS
THINK THAT A MASSIVE COMET COULD
SOMEDAY STRIKE EARTH, CAUSING A
MEGA DISASTER. IT MAY HAVE HAPPENED BEFORE.
4,800 YEARS AGO, A COMET MAY
HAVE KILLED MORE THAN 50% OF THE
POPULATION. IRONICALLY, MANY SCIENTISTS
BELIEVE THAT COMETS MAY HAVE
BROUGHT TO EARTH THE BASIC
ELEMENTS THAT MAKE LIFE POSSIBLE.
DURING THE TIME IT WAS BEING
FORMED, THE PLANET WAS VERY HOT
AND VERY DRY. SO THE QUESTION THAT HAS LONG
PUZZLED SCIENTISTS IS, WHERE DID
OUR WATER COME FROM?
ONE THEORY IS THAT COMETS STRIKING EARTH BILLIONS OF YEARS
AGO PROVIDED THE WATER THAT
WOULD EVENTUALLY MAKE UP THE
PLANET'S OCEANS AND SEAS. IN THE YEAR 2000, COMET LINEAR
BROKE APART AS IT PASSED BY THE
SUN.
INFRARED-SPECTRUM ANALYSIS REVEALED THAT THE COMET WAS
LIKELY MADE UP OF WATER IN THE
FORM OF ICE.
SOME SCIENTISTS BELIEVE THAT COMETS MAY HAVE ALSO DISPERSED
COMPLEX ORGANIC MOLECULES THAT
COULD HAVE BECOME THE FIRST CELL
MEMBRANES ON EARTH. >> COMETS CAME IN AND PROVIDED
MUCH OF THE WATER THAT'S IN OUR
OCEANS TODAY AND MUCH OF THE
WATER THAT'S IN OUR BODIES TODAY.
AND COMETS MAY ALSO HAVE BROUGHT
TO THE EARLY EARTH MUCH OF THE
CARBON-BASED MOLECULES THAT IS NECESSARY FOR LIFE, SO WITHOUT
COMETARY BOMBARDMENTS, IT'S
UNLIKELY THAT LIFE WOULD HAVE
FORMED ON EARTH. SO WE OWE OUR VERY EXISTENCE TO
THESE OBJECTS.
>> Narrator: FROM THE TIME THEY
WERE FORMED 4.6 BILLION YEARS AGO, COMETS AND ASTEROIDS HAVE
CRASHED ONTO EARTH AND ITS MOON
COUNTLESS TIMES.
THOUGH THE MOON'S CRATERED SURFACE BEARS WITNESS TO THAT
VIOLENT PAST, EARTH'S IMPACT
CRATERS ARE LESS APPARENT. >> IN THE COURSE OF TIME, THE
EARTH HAS ACTUALLY SUFFERED MORE
IMPACTS THAN THE MOON HAS
BECAUSE IT HAS A BIGGER AREA THAN THE MOON DOES. BUT WE SEE MANY FEWER CRATERS ON
THE EARTH.
THAT'S BECAUSE EROSION,
TECTONICS, ALL THESE PROCESSES THAT ARE SO ACTIVE ON THE EARTH
BUT LACKING ON THE MOON, HAVE
ERASED THE CRATERS.
>> Narrator: EVEN ON DRY LAND, CRATERS ARE DIFFICULT TO
IDENTIFY.
>> IMPACT CRATERS ARE ONE OF THE
RAREST OF THE LANDFORMS ON THE EARTH.
IN FACT, ONLY ABOUT 170 BONA
FIDE IMPACT CRATERS ARE
RECOGNIZED ON THE EARTH. >> Narrator: OF THESE 170 IMPACT
CRATERS, NONE IS LOCATED IN DEEP
OCEAN WATERS, EVEN THOUGH OCEANS
COVER 70% OF OUR PLANET. BUT THERE MAY BE A NUMBER OF
MISSING CRATERS ON THE SEAFLOOR.
SO, HOW DO WE BEGIN LOOKING FOR
EVIDENCE OF A MASSIVE COMET IMPACT IN THE OCEANS?
SCIENTISTS ARE TACKLING THE
SEARCH ON MANY FRONTS --
EVALUATING SATELLITE IMAGES TO IDENTIFY CRATER STRUCTURES ALL
OVER THE WORLD AND TO LOCATE
SOIL DEPOSITS LEFT ON THE COASTS
BY MEGA TSUNAMIS... STUDYING COMPUTER MODELS TO
PREDICT THE POSSIBLE EFFECTS OF
OCEANIC IMPACTS...
USING TELESCOPES AND SPACE PROBES TO STUDY COMETS AND LEARN
ABOUT THEIR COMPOSITION AND LIFE
CYCLES...
AND ANALYZING SEAFLOOR AND COASTAL SEDIMENT SAMPLES UNDER
ELECTRON MICROSCOPES.
DR. ABBOTT STARTED HER SEARCH
FOR EVIDENCE OF THIS CATASTROPHIC COMET IMPACT IN THE
INDIAN OCEAN. >> ONE REASON WHY I FOCUSED ON
THE INDIAN OCEAN WAS BECAUSE OF
BRUCE MASSE'S WORK WHERE HE'S
COMPILED ORAL HISTORIES, AND WHAT HE DETERMINED WAS THAT THE
CENTER OF THIS LARGE DELUGE
EVENT WAS IN THE INDIAN OCEAN. >> Narrator: THE FIRST PHYSICAL
EVIDENCE OF THIS ALLEGED CRATER
WAS FOUND NOT IN THE OCEAN
ITSELF BUT ON THE BEACHES OF AUSTRALIA AND MADAGASCAR --
MASSIVE SEDIMENTARY DEPOSITS
CALLED CHEVRONS, SOME OF THEM
THE SIZE OF MANHATTAN. >> THE CHEVRON DUNE IS ALMOST
LIKE SWASH ON A BEACH.
YOU GET A WAVE COMING IN, AND IT
LEAVES AN OUTLINE. THEY'RE ROUGHLY V-SHAPED, BUT IF
YOU TAKE THE V-SHAPED DUNE
COMING IN, ITS TREND POINTS
BACK TOWARDS THE SOURCE. >> Narrator: THAT SOURCE COULD
HAVE BEEN A MASSIVE IMPACT IN
THE INDIAN OCEAN.
>> WHEN A BIG IMPACTOR COMES IN AND HITS THE OCEAN FLOOR, IT
DOESN'T MAKE JUST A CRATER IN
THE SEAFLOOR.
IT ALSO MAKE A CRATER -- AN EVEN WIDER CRATER -- IN THE
WATER. AND THEN WHAT HAPPENS IS, THIS
WATER HAS TO FILL IN THE HOLE,
AND IT CRASHES BACK IN, AND THEN
IT OSCILLATES BACK AND FORTH SEVERAL TIMES.
>> Narrator: SUCH AN IMPACT
WOULD HAVE CREATED COLOSSAL
WAVES CALLED MEGA TSUNAMIS. >> SO, IF WE'RE TALKING ABOUT A
DIAMETER OF THREE MILES FOR THE
IMPACTOR, TYPICALLY, A LARGE
IMPACTOR COMING IN LIKE THAT COULD PRODUCE A WAVE THAT WAS
INITIALLY ABOUT THREE MILES
HIGH.
>> Narrator: BY THE TIME THEY REACHED THE COAST OF MADAGASCAR,
THE WAVES STILL WOULD HAVE BEEN
COLOSSAL, CREATING THE CHEVRONS
BY DEPOSITING LARGE AMOUNTS OF COASTAL SEDIMENT AND IMPACT
DEBRIS.
>> IN THE MADAGASCAR CHEVRONS,
WE FOUND A NUMBER OF FEATURES THAT WE THINK ARE MATERIALS THAT
ARE DERIVED FROM AN OCEANIC
IMPACT.
>> Narrator: SUCH AS THESE DEEP, COLD-WATER MICROFOSSILS CALLED
FORAMINIFERA.
>> THIS IS A PICTURE OF ONE OF
THESE BOTTOM-LIVING FORAMINIFERA, AND NOTE THAT ALL
THE MAGNESIUM, WHICH IS IN BLUE,
IS MOSTLY JUST RIGHT ON THE
OUTSIDE OF THE CHAMBERS. AND WE THINK THAT THIS MAY BE
DUE TO BOILING OF SEAWATER IN
THE CHAMBERS RIGHT AFTER THE
IMPACT. >> Narrator: BUT WHERE IN THE
INDIAN OCEAN IS THE IMPACT
CRATER ITSELF?
SATELLITE IMAGERY MAY PROVIDE THE ANSWER.
THE SURFACE OF THE SEA ACTUALLY
FOLLOWS ROUGHLY THE PROFILE OF
THE SEAFLOOR. UNDERWATER SEA MOUNTS AND
DEPRESSIONS AFFECT THE
GRAVITATIONAL PULL OF EARTH ON
THE OCEAN'S SURFACE, SO WE CAN FIND HOLES IN THE SEAFLOOR BY
MEASURING THE PROFILE OF THE SEA
SURFACE WITH SATELLITES.
>> I TOOK THE CHEVRON DUNES, AND I USED THEIR TRENDS TO LOOK FOR
POSSIBLE CRATERS. THE DIRECTION THAT THE CHEVRON
DUNES POINT CONVERGES VERY
CLOSELY ON A LOCATION WHERE YOU
HAVE A HOLE IN THE OCEAN FLOOR -- A NICE, ROUND HOLE. >> Narrator: THIS HOLE IS
930 MILES SOUTHEAST OF
MADAGASCAR, AN 18-MILE-WIDE
STRUCTURE 13,000 FEET UNDERWATER KNOWN AS BURCKLE CRATER.
BUT A ROUND HOLE IN THE SEAFLOOR
IS NOT ENOUGH PROOF OF A COMET
IMPACT. DR. JAY MELOSH, A PLANETARY
SCIENTIST AT THE UNIVERSITY OF
ARIZONA, IS NOT INVOLVED IN
DR. ABBOTT'S RESEARCH, BUT HE EXPLAINS THAT GEOLOGICAL PROOF
OF A COMET STRIKE WOULD BE FOUND
AT THE IMPACT SITE. >> WHEN A COMET STRIKES THE
EARTH AT, SAY, 30 MILES A
SECOND, IT CAUSES HUGE
PRESSURES. IN THE PROCESS OF HITTING THE
ROCKS, THOSE ROCKS ARE CHANGED
IN A WAY THAT NO OTHER PROCESS
ON THE EARTH CAN. IF WE CAN FIND THAT CHANGED
MINERAL IN THE IMPACT SITE,
WE'RE SURE THAT IT'S AN IMPACT.
>> Narrator: SHIPS CRISSCROSS THE WORLD'S OCEANS, GATHERING
DEEP-SEAFLOOR SAMPLES.
EVERY ONE OF THOSE DOTS
REPRESENTS AN AREA WHERE SCIENTISTS HAVE COLLECTED
DEEP-SEA CORE SAMPLES...
WHICH ARE SOIL SAMPLES EXTRACTED
FROM BENEATH THE OCEAN FLOOR. THOUSANDS OF THESE CORES ARE
STORED AT THE LAMONT-DOHERTY
EARTH OBSERVATORY IN NEW YORK,
WHERE DR. ABBOTT STUDIES THEM. >> THIS CORE IS FROM THE
SOUTHWEST INDIAN OCEAN.
IT'S FROM THE VICINITY OF
BURCKLE CRATER, AND YOU CAN SEE THAT IT'S A FAIRLY DARK COLOR.
THE DARK COLOR IS BECAUSE IT'S
FROM QUITE DEEP WATER, ABOUT
4,800 METERS DEEP. THIS IS ENOUGH, I THINK.
>> OKAY.
>> Narrator: DR. ABBOTT ANALYZES
THE SEAFLOOR SAMPLES UNDER A SCANNING ELECTRON MICROSCOPE
WITH DREXEL UNIVERSITY'S
DIRECTOR OF MICROSCOPY,
DEE BREGER. >> WHEN COMETS OR ASTEROIDS HIT
THE BOTTOM OF THE SEA, THEY TEND
TO VAPORIZE OR MELT MATERIAL
EITHER FROM THE ROCK THAT THEY'VE HIT OR THE IMPACTOR
ITSELF, WHICH CONDENSES INTO
SUBMICROSCOPIC SPLASHES OF METAL
THAT ARE SHOT INTO GRAINS OF SEDIMENT, INTO MICROFOSSILS,
INTO WHATEVER IS DOWN THERE AT
THE BOTTOM OF THE SEA, IN
MICROSCOPIC AMOUNTS. >> WHAT WE FOUND IN THIS SAMPLE
WERE LITTLE BITS OF CRUSHED
ROCK.
THESE PIECES OF ROCK LOOKED AS IF THEY'D BEEN HIT WITH A
HAMMER, AND THEN ON THE ROCK, WE
FOUND TINY BITS OF METAL,
NICKEL-RICH METAL. AND NICKEL IS NOT VERY COMMON ON
THE EARTH, SO WE THINK THAT THIS
NICKEL IS BITS OF THE IMPACTOR
THAT WERE VAPORIZED. >> I DON'T NECESSARILY SEE A
SPLASH YET.
>> Narrator: STILL, DR. ABBOTT
NEEDS MORE EVIDENCE TO PROVE THAT BURCKLE CRATER WAS CREATED
BY A COMET IMPACT.
>> WHAT WE HOPE TO LEARN FROM
THIS PIECE OF DEEP-SEA SEDIMENT IS WHAT'S THE SOURCE OF THE
IMPACT THAT PRODUCED BURCKLE
CRATER?
WE REALLY DON'T KNOW ENOUGH ABOUT COMETS AND ASTEROIDS TO BE
SURE RIGHT NOW IF WE CAN TELL.
>> Narrator: WE MAY NOT KNOW
ENOUGH ABOUT COMETS, BUT WE KNOW THEY ARE OUT THERE ON THE
FRINGES OF THE SOLAR SYSTEM,
BILLIONS OF THEM, AND THEY ARE
JUST WAITING FOR A PASSING STAR'S GRAVITATIONAL FORCE TO
LAUNCH ONE OF THEM ON A
CATASTROPHIC COLLISION COURSE
WITH EARTH. >> Narrator: EVER SINCE MAN
FIRST NOTICED THESE FIERY
OBJECTS IN THE NIGHT SKY, COMETS
HAVE INSPIRED WONDER AND FEAR. >> PEOPLE HAVE BEEN OBSERVING
COMETS FOR THOUSANDS OF YEARS.
THEY FLY BY, WE LOOK AT THEM,
AND WE SAY, "WHOA! YOU KNOW, SOMETHING IS HAPPENING
THAT'S VERY UNUSUAL." >> Narrator: THEIR ENIGMATIC
HISTORY DATES BACK TO THE DAWN
OF OUR SOLAR SYSTEM, 4.6 BILLION
YEARS AGO. OUR SOLAR SYSTEM EMERGED FROM A
CLOUD OF GAS AND DUST IN MOTION.
FROM IT, THE HOT, INNER
SOLAR-SYSTEM PLANETS -- MERCURY, VENUS, EARTH, AND MARS -- WERE
FORMED, LEAVING THE LEFTOVER
ROCKY PIECES OF THAT PROCESS,
THE ASTEROIDS, IN ORBIT JUST BEYOND MARS, IN THE ASTEROID
BELT.
THE COOLER, OUTER SOLAR SYSTEM
PLANETS -- JUPITER, SATURN, URANUS, AND NEPTUNE -- FORMED,
YIELDING AS REMNANTS THE ICY
OBJECTS WE CALL COMETS.
>> THERE'S THREE BASIC PARTS TO AN ACTIVE COMET.
THE TAIL CAN BE EITHER GAS OR
DUST, AND IT'S TYPICALLY
MILLIONS OF MILES IN LENGTH. THE COMA, OR ATMOSPHERE, CAN BE
HUNDREDS OF THOUSANDS OF MILES
IN DIAMETER. BUT THE NUCLEUS TYPICALLY IS
ONLY A FEW MILES IN DIAMETER,
AND THAT IS THE HEART OF THE
COMET -- THE ICES AND THE DUST IN SOLID FORM. >> Narrator: BILLIONS OF YEARS
LATER, THOUSANDS OF OBJECTS
LINGER IN WHAT ASTRONOMERS CALL
NEAR-EARTH PROXIMITY -- THAT IS, WITHIN 120 MILLION MILES, WHICH
IS CLOSE ON A COSMIC SCALE.
THERE ARE TWO TYPES OF
NEAR-EARTH OBJECTS THAT CONCERN ASTRONOMERS.
>> WE HAVE THE ASTEROIDS, WHICH
ARE FAR MORE NUMEROUS THAN THE
COMETS, BUT WE CAN DISCOVER THEM 20, 30 YEARS IN ADVANCE OF ANY
THREATENING IMPACT.
THE COMETS, ON THE OTHER HAND,
ARE A DIFFERENT STORY. >> Narrator: UNLIKE THE MORE
PREDICTABLE ASTEROIDS, COMETS
MAY APPEAR WITH DANGEROUSLY
SHORT WARNING TIMES. >> IF WE DO FIND A COMET THAT'S
ON AN EARTH-THREATENING
TRAJECTORY, WE WOULD ONLY HAVE A
FEW MONTHS TO DEAL WITH IT. >> Narrator: A COMET IMPACT IN
THE NEAR FUTURE IS VERY
UNLIKELY.
BUT IT IS A REAL THREAT, MADE MORE CRITICAL BY HOW LITTLE WE
KNOW ABOUT THESE CELESTIAL
MISSILES. >> WE KNOW A LOT ABOUT ASTEROIDS
FROM STUDYING METEORS FOR MANY,
MANY YEARS, BUT THERE'S NOT
NEARLY AS MUCH DATA ON COMETS OR HOW THEY'RE PUT TOGETHER
PHYSICALLY. >> Narrator: AS MYSTERIOUSLY AS
THEY APPEAR, COMETS DO NOT
MATERIALIZE OUT OF NOWHERE.
THEY SEEM TO HAVE TWO COSMIC HOMES.
THE SO-CALLED SHORT-PERIOD
COMETS, SUCH AS THE FAMOUS COMET
HALLEY, COME FROM AN AREA JUST BEYOND THE ORBIT OF PLUTO CALLED
THE KUIPER BELT.
>> THE KUIPER BELT COMETS, WE
HAVE MUCH GREATER LUCK TRACKING THEM, KNOWING WHERE THEY ARE,
HAVING THEM REPEAT SO THAT
WE'RE, "OKAY, THIS IS THE SAME
ONE WE'VE SEEN FIVE YEARS AGO." >> Narrator: BUT THERE IS A MORE
INTRIGUING COLLECTION OF COMETS
WHICH ORIGINATES MUCH FARTHER
AWAY FROM EARTH AND COULD POSE A GREATER HAZARD.
>> THE SECOND SOURCE OF COMETS
IS THE SO-CALLED OORT CLOUD,
WHICH EXTENDS OUT TO THE VERY EDGE OF OUR SOLAR SYSTEM,
HALFWAY TO THE NEAREST STAR.
AND THIS IS A SPHERICAL
DISTRIBUTION OF COMETS. >> Narrator: THERE ARE BILLIONS
OF THESE SO-CALLED LONG-PERIOD
COMETS IN THE OORT CLOUD.
>> THE OORT CLOUD TENDS TO SEND COMETS IN AT RANDOM.
THEY COME IN FROM ALL
DIRECTIONS, AND WE NEVER KNOW
WHERE THEY'RE GONNA COME FROM AND WHEN THEY'RE GONNA COME BY.
AND MOST OF THOSE OORT CLOUD
COMETS COME IN AND GO OUT AND WE
NEVER SEE THEM AGAIN. >> Narrator: THEIR SIZE AND
SPEED MAKE THEM CAPABLE OF
MULTIMEGATON IMPACTS, POWERFUL
ENOUGH TO CAUSE A MASS EXTINCTION IF THEY HIT EARTH.
>> LET'S THINK OF OURSELVES
RIDING ALONG ON THE COMET AS
ITS LIFETIME PROGRESSES. IT STARTS OUT IN THE OORT CLOUD,
AND AT THAT DISTANCE, OF COURSE,
THE SUNLIGHT IS SO REMOTE THAT
THESE ICES ARE STILL ROCK-HARD. AND SO YOU'VE GOT A JET-BLACK,
ICY DUST BALL IN SPACE THAT
SLOWLY IS PERTURBED OUT OF THE
OORT CLOUD BY A PASSING STAR, PERHAPS.
>> Narrator: INITIALLY SOME
COMETS TRAVEL SLOWER THAN MOST
AIRPLANES. >> IT'S A MILLION-YEAR VOYAGE,
AND THE VAST MAJORITY OF IT IS
SPENT IN COMPLETE DARKNESS AND
COMPLETE DEEP FREEZE OF SPACE. >> Narrator: NEAR JUPITER, THE
COMET STARTS TO FEEL THE SUN'S
HEAT AND WAKES UP, TRANSFORMING
INTO A HIGH-SPEED MISSILE, ACCELERATING TO MORE THAN 70,000
MILES PER HOUR DUE TO THE
GRAVITATIONAL ATTRACTION OF THE
SUN AND THE PLANETS. >> AT THAT POINT, THE ICES --
MOSTLY WATER ICE -- START
VAPORIZING, AND THE DUST
PARTICLES WITHIN THE VAPOR STREAM START REFLECTING
SUNLIGHT, AND THAT BEGINS TO
SHOW ITSELF AS WHAT WE CALL A
COMET. >> Narrator: THIS PROCESS MAKES
IT DIFFICULT TO STUDY THE
COMPOSITION OF THE COMET ITSELF.
>> THE PROBLEM WITH STUDYING THE HEART OF A COMET, THE NUCLEUS,
IS THAT ONCE THE COMET GETS INTO
THE INNER SOLAR SYSTEM WHERE WE
CAN GET A GOOD LOOK AT IT, MOTHER NATURE STARTS THROWING
OFF GAS AND DUST FROM THESE
COMETARY NUCLEI.
AND IT EFFECTIVELY HIDES THE COMETARY NUCLEUS, AND SO TO
UNDERSTAND WHAT IS THE HEART OF
A COMET, YOU HAVE TO SEND A
SPACECRAFT. >> Narrator: WE HAVE LAUNCHED A
NUMBER OF MISSIONS TO STUDY
COMETS SINCE 1978.
BUT TWO RECENT MISSIONS HAVE BEEN THE MOST SUCCESSFUL TO
DATE.
>> THE DEEP IMPACT MISSION
ACTUALLY RAN INTO COMET TEMPEL ONE IN JULY OF 2005, AND THE
STARDUST SPACECRAFT FLEW CLOSELY
PAST COMET WILD TWO, AND BROUGHT
BACK TO EARTH SOME OF THE DUST FROM THAT COMET.
SO THOSE TWO MISSIONS HAVE
REALLY ENABLED US TO UNDERSTAND
THE NATURE OF A COMETARY NUCLEUS.
>> Narrator: THE FINDINGS
REVEALED INFORMATION ABOUT ITS
COMPOSITION. >> THE FACT THAT THEY'RE JET
BLACK, THEY'RE ICY DUST BALLS
COVERED WITH A LAYER OF SILICATE
DUST -- TALCUM-POWDER-LIKE DUST. OBJECTS THAT ARE A FEW MILES IN
DIAMETER, MUFFIN-SHAPED --
EASILY BROKEN APART, VERY
FRAGILE OBJECTS, AND THE REMNANTS OF THE EARLY SOLAR
SYSTEM FORMATION PROCESS.
>> Narrator: EVEN THOUGH COMETS
MAY BE FRAGILE, THEIR SPEED, SIZE, AND UNPREDICTABILITY CAN
MAKE THEM VERY LETHAL THREATS.
THEREFORE, SCIENTISTS HOPE THAT
THE NEXT MISSION WILL REVEAL EVEN MORE ABOUT THESE COSMIC
STEALTH MISSILES.
THE NEW EUROPEAN MISSION ROSETTA
IS ALREADY ON ITS WAY TO COMET CHURYUMOV-GERASIMENKO.
WHEN IT ARRIVES IN NOVEMBER OF
2014, IT WILL PERFORM A SERIES
OF MANEUVERS CULMINATING IN THE FIRST LANDING ON THE SURFACE OF
A COMET IN FLIGHT. >> WE'RE GONNA FLY OUT AND MEET
THE COMET NEAR THE ORBIT OF
JUPITER AND ESCORT THE COMET IN
ALL THE WAY PAST THE SUN AND OUT ON ITS OUTBOUND LEG, GETTING A
CHANCE TO STUDY IT FOR MONTHS
AND MONTHS, WATCHING IT AS ITS
ACTIVITY UNFOLDS. >> Narrator: BUT BEFORE WE CAN
IDENTIFY WHICH COMETS MAY POSE A
THREAT TO OUR PLANET, WE HAVE TO
FIND THEM FIRST. >> Narrator: THE FIRST STEP TO
PROTECT OUR PLANET AGAINST A
LETHAL COMET IS TO FIND IT
BEFORE IT FINDS US. >> COMETS ARE DISCOVERIES.
THEY ARE THINGS THAT YOU'RE NOT
EXPECTING TO FIND IN ONE
PARTICULAR SPOT OR ANOTHER. SO HAVING A TELESCOPE THAT LETS
YOU LOOK AT A LARGE AREA OF SKY
AT ONCE IS ACTUALLY MUCH MORE
BENEFICIAL THAN SOMETHING, SAY, LIKE THE HUBBLE TELESCOPE, WHICH
IS REALLY ONLY STARING AT A VERY
TINY PIECE OF SKY, BUT IN A LOT
OF DETAIL. >> Narrator: NEW WIDE-FIELD
TELESCOPES WILL HELP US WATCH
THE SKIES FOR MENACING COMETS.
THE LARGE-SYNOPTIC-SURVEY TELESCOPE, LSST, WILL SEE FIRST
LIGHT IN 2014.
IT WILL PROVIDE DIGITAL IMAGING
OF FAINT ASTRONOMICAL OBJECTS, SUCH AS DISTANT COMETS, WITH A
3,000-MEGAPIXEL CAMERA FROM ITS
VANTAGE POINT ATOP CERRO PACHóN
IN CHILE. >> THE LSST WILL ACTUALLY BE
ABLE TO TAKE A COMPLETE SNAPSHOT
OF THE SKY EVERY FEW DAYS, AND
IT WILL KEEP REPEATING THAT OVER AND OVER AGAIN.
SO BY STACKING THESE FULL-SKY
PICTURES UP ONE ON TOP OF THE
OTHER, ASTRONOMERS CAN LOOK TO SEE IF ANYTHING IS MOVING.
>> Narrator: ON AUGUST 7th OF
2006, USING THIS FOUR-PICTURE
TIME-LAPSE SEQUENCE, ASTRONOMER ROBERT McNAUGHT DISCOVERED THE
COMET NOW BEARING HIS NAME.
THE FAINT AND FUZZY SPOT MOVING
WITHIN THE CIRCLE IS COMET McNAUGHT. >> ONCE WE FIND THESE OBJECTS IN
THE INNER SOLAR SYSTEM, WE HAVE
TO COMPUTE ORBITS FOR THEM TO BE
ABLE TO PREDICT WHERE THEY'LL BE IN THE FUTURE. >> Narrator: ASTEROIDS ARE
EASIER TO FIND AND TRACK BECAUSE
THEY ARE INACTIVE, AND THEIR
ORBITS ARE AFFECTED ONLY BY THE NEIGHBORING PLANETS.
>> COMETS, ON THE OTHER HAND,
HAVE AN ADDITIONAL PROBLEM WITH
THEM BECAUSE, WHEN THEY GET INTO THE INNER SOLAR SYSTEM, THEY
START THRUSTING TOWARD THE SUN,
AND THAT PUSHES THE COMET IN THE
OPPOSITE DIRECTION. >> Narrator: THIS MAY MODIFY
THEIR TRAJECTORY AS THEY FLY,
LIKE A ROCKET ENGINE MIGHT,
MAKING IT DIFFICULT TO CALCULATE THEIR ORBITS ACCURATELY.
ANOTHER PROBLEM IS THAT COMETS
ARE VIRTUALLY INVISIBLE UNTIL
THEY REACH JUPITER AND START EJECTING GAS AND DUST.
>> AND IT ONLY TAKES NINE MONTHS
TO GET FROM THE ORBIT OF JUPITER
TO THE ORBIT OF EARTH. IT WOULD TAKE A FEW MONTHS TO
DETERMINE ITS ORBIT AND TO
DETERMINE THAT IT IS A THREAT,
AND THEN WE'D ONLY HAVE A COUPLE OF MONTHS TO DO SOMETHING ABOUT
IT.
>> Narrator: IT COULD BE WORSE.
SOME COMETS ARE DISCOVERED CLOSER TO EARTH.
COMET McNAUGHT WAS SPOTTED IN
AUGUST OF 2006, ONLY 4 MONTHS
BEFORE IT PASSED BY EARTH'S ORBIT IN NOVEMBER THAT SAME
YEAR.
SCIENTISTS AND ENGINEERS ARE
WORKING ON WAYS TO DEFLECT OR DESTROY AN ASTEROID ON A
COLLISION COURSE WITH EARTH,
FROM NUCLEAR WEAPONS TO GRAVITY
TRACTORS. BUT TODAY, THERE IS LITTLE WE
CAN DO TO DEFEND OURSELVES
AGAINST AN INCOMING COMET.
>> IN THE UNLIKELY EVENT THAT WE DO FIND A COMET THAT'S ON AN
EARTH-THREATENING TRAJECTORY
AND IT'S LARGE -- SAY, TWO MILES
OR LARGER -- THERE'S NOT A GREAT DEAL WE CAN DO, FRANKLY.
THAT'S THE BAD NEWS.
THE GOOD NEWS IS IT'S NOT VERY
LIKELY TO HAPPEN. >> Narrator: TO DATE,
DAVID LEVY HAS DISCOVERED 22
COMETS FROM HIS OBSERVATORY IN
THE ARIZONA DESERT. >> EVERY TIME A COMET IS
DISCOVERED, THERE'S ALWAYS A
LITTLE HICCUP THAT HAPPENS.
IS THIS COMET ONE THAT CAN ENDANGER THE EARTH?
THE ONE THAT I FOUND A FEW
MONTHS AGO IS ONE THAT COMES BY
EVERY FIVE YEARS, AND THERE'S A CHANCE THAT, AT ONE OF ITS
PASSAGES, IT COULD THREATEN THE
EARTH. WE'RE NOT SURE ABOUT THAT.
WE DON'T KNOW IT AS WELL AS WE'D
LIKE TO.
>> Narrator: IN 1992, MR. LEVY, TOGETHER WITH DR. EUGENE AND
CAROLYN SHOEMAKER DISCOVERED THE
NOW-FAMED SHOEMAKER-LEVY 9 COMET
THAT PLUNGED INTO JUPITER IN 1994.
>> THE IMPORTANT THING TO
REMEMBER ABOUT COMETS IS THAT
THEY'RE -- THEY'RE LIKE CATS. THEY BOTH HAVE TAILS, AND THEY
BOTH DO PRECISELY WHAT THEY WANT
TO DO.
IN SOME WAYS, COMET HUNTING IS AN ART, NOT A SCIENCE.
>> Narrator: FROM THE
INDIAN OCEAN 4,800 YEARS AGO, TO
THE PACIFIC COAST OF SAN FRANCISCO TODAY, WE CAN ONLY
IMAGINE WHAT A LARGE COMET
STRIKE WOULD UNLEASH IF IT
HAPPENED NOW. >> THERE'S NO DOUBT THAT THERE'S
GONNA BE DRAMATIC EFFECTS ON THE
EARTH, ON THE EARTH'S SURFACE,
ON THE CLIMATE, AND THAT ARE GOING TO AFFECT LIFE.
>> Narrator: A THREE-MILE-WIDE
COMET STRIKE COULD KILL MILLIONS
OF PEOPLE. EXACTLY HOW THAT WOULD HAPPEN IS
HARD TO PREDICT.
>> FORTUNATELY, WE'VE NEVER SEEN
A LARGE COMET STRIKE THE EARTH, BUT WE CAN WORK OUT WHAT HAPPENS
BY USING THE LAWS OF PHYSICS. WE CAN TAKE THOSE LAWS, DISTILL
THEM DOWN INTO A COMPUTER
PROGRAM, AND PREDICT WHAT EVENTS
WILL HAPPEN WHEN A MILE-WIDE COMET SLAMS INTO THE EARTH AND
MAKES A CRATER PERHAPS 20 MILES
IN DIAMETER.
>> Narrator: FAMED INSTITUTIONS SUCH AS THE LOS ALAMOS NATIONAL
LABORATORY ARE LOOKING AHEAD. >> WE HAVE, IN FACT, RIGHT NOW
VERY LARGE THREE-DIMENSIONAL
COMPUTER-CODE CAPABILITIES THAT
CAN HELP US, AS A NATION, IMPROVE OUR DETECTION, OUR
ASSESSMENT, OF CATASTROPHIC
IMPACTS SUCH AS A COMETARY
IMPACT OFF THE COAST OF SAN FRANCISCO. >> Narrator: NEXT, WITH DATA
COMPILED BY DR. ABBOTT AND
DAMAGE ESTIMATES BASED UPON AN
IMPACT-EFFECT CALCULATIONS PROGRAM, WE CAN DEPICT A
SCENARIO OF A THREE-MILE-WIDE
COMET CRASHING INTO EARTH.
WITH LITTLE WARNING AND NO WAY TO STOP THIS INTRUDER, MILLIONS
OF PEOPLE COULD FIND THEMSELVES
IN THE MIDDLE OF A GLOBAL MEGA
DISASTER. >> Narrator: COULD A MASSIVE
COMET CRASH INTO EARTH AGAIN?
SOME DAY, THIS SCIENCE-FICTION
SCENARIO COULD BECOME A DEVASTATING REALITY.
BASED ON DATA GATHERED BY
DR. DALLAS ABBOTT AND
CALCULATIONS PERFORMED WITH THE UNIVERSITY OF ARIZONA'S
IMPACT-EFFECT-CALCULATOR
PROGRAM, IT MIGHT UNFOLD LIKE
THIS. A COMET STARTED ITS JOURNEY
MILLIONS OF YEARS AGO ON THE
DISTANT EDGE OF OUR SOLAR
SYSTEM. IT IS NOW NEAR JUPITER.
THE STEALTHY, ANCIENT TRAVELER
AWAKENED BY THE APPROACHING SUN
STARTS JETTING DUST AND GASSES FROM ITS ICY NUCLEUS.
IT IS FOUR MONTHS AWAY FROM ITS
TARGET -- EARTH.
2:00 A.M. AT THE MAUNA KEA OBSERVATORIES IN HAWAII.
ASTRONOMERS IDENTIFY THE FAINT
OPTICAL SIGNATURE OF WHAT MAY BE
A NEW COMET... AS DIM AS COMET McNAUGHT'S IGE
WHEN IT WAS DISCOVERED IN 2006.
OTHER ASTRONOMERS AROUND THE
WORLD CONFIRM THE SIGHTING. IT IS A NEW COMET, AND IT IS
APPROACHING MARS FAST.
THE MINOR PLANET CENTER IN
CAMBRIDGE, MASSACHUSETTS, BEGINS TO CALCULATE ITS ORBIT.
IT WILL TAKE SCIENTISTS A COUPLE
OF MONTHS OR MORE TO DETERMINE
IF IT COULD HIT EARTH. NEAR MARS' ORBIT, THE TRAVELER
IS NOW A DAZZLING SIGHT, WITH A
GROWING TAIL OF LIGHT DASHING
TOWARD EARTH AT OVER 50,000 MILES PER HOUR.
IT IS CONFIRMED.
THE OBJECT IS A LONG-PERIOD
COMET WITH A TRAJECTORY THAT WILL CAUSE IT TO HIT EARTH IN 30
DAYS.
ALERTS ARE SENT ALL OVER THE
WORLD, BUT TIME IS RUNNING OUT. GOVERNMENTS AND INTERNATIONAL
SPACE AND MILITARY ORGANIZATIONS
SCRAMBLE TO DECIDE ON A COURSE
OF ACTION. IT'S TECHNOLOGICALLY MUCH MORE
DIFFICULT TO DEAL WITH A COMET
THAN IT IS AN ASTEROID. >> Narrator: SHOOTING IT DOWN IS
NOT AN OPTION.
IT MAY COMPOUND THE PROBLEM BY
CREATING A COLLECTION OF FRAGMENTS.
DIVERTING ITS TRAJECTORY WITH A
SPACECRAFT IS NOT POSSIBLE.
THERE IS NOT ENOUGH TIME TO PREPARE AND LAUNCH SUCH A
MISSION.
NOW, ABOUT 2 MILLION MILES AWAY
FROM EARTH, THE COMET SPEEDS AT MORE THAN 100,000 MILES PER
HOUR.
SCIENTISTS NARROW THE PROBABLE
IMPACT ZONE TO AN OFFSHORE AREA NEAR SAN FRANCISCO.
THE COMET IS ABOUT TO COLLIDE
WITH OUR PLANET'S MOST EFFECTIVE
SHIELD, THE ATMOSPHERE, BUT IT WILL PROVIDE NO DEFENSE AT ALL.
>> A LARGE COMET SEVERAL MILES
IN DIAMETER WOULD SIMPLY PUNCH
RIGHT THROUGH THE ATMOSPHERE, AND IT WOULDN'T MATTER THAT THE
COMET IS FRAGILE AND UNDERDENSE
AND POROUS.
>> Narrator: BRIDGES AND FREEWAYS ARE JAMMED AS A
PANICKED POPULATION TRIES TO
FLEE THE CITY, BUT IT IS TOO
LATE. THE THREE-MILE-WIDE COMET HITS
THE PACIFIC OCEAN 100 MILES WEST
OF SAN FRANCISCO...
WITH MORE THAN 30 MILLION MEGATONS OF ENERGY. >> WHEN IT IMPACTS THE OCEAN'S
SURFACE, IT IS GOING TO
ESSENTIALLY VAPORIZE THE WATER
ALMOST IMMEDIATELY. THE IMPACT UNLEASHES A BLAST OF
THERMAL RADIATION TOWARD THE
CITY.
>> YOU'RE TALKING ABOUT A MINIMUM OF TEMPERATURES AROUND
1,500 KELVIN, SO ANYONE WHO'S
OUTSIDE WHEN THAT EVENT OCCURS
WOULD ESSENTIALLY BE VAPORIZED ALMOST.
>> Narrator: WOODEN STRUCTURES,
DRY GRASS, AND BRUSH ALL IGNITE
IN A FLASH. FLAMES BURST OUT AROUND THE
CITY.
AS MORE THAN 7 MILLION PEOPLE IN
THE BAY AREA ARE SCORCHED BY THE LETHAL HEAT, A 9.0 EARTHQUAKE
CAUSED BY THE COMET'S IMPACT
SHATTERS STRUCTURES AND
BUILDINGS ALL OVER SAN FRANCISCO.
THE BAY BRIDGE COLLAPSES.
THE GOLDEN GATE BRIDGE YIELDS TO
THE INEXORABLE POWER OF NATURE. ENTIRE DISTRICTS IN THE CITY
CAVE IN AS THE GROUND LIQUIFIES
UNDER THEIR FOUNDATIONS.
CRACKS APPEAR ON THE GROUND, TRANSFORMING THE LANDSCAPE.
AS THE MINUTES TICK BY IN SLOW
MOTION, THREE-INCH FRAGMENTS OF
DEBRIS FROM THE SEAFLOOR PUMMEL THE DEFENSELESS CITY.
IN THE MIDST OF CHAOS AND
DESTRUCTION, A MOMENT OF EERIE
SILENCE PRECEDES THE SONIC BANG. [ EXPLOSION ]
THE DEAFENING AIR BLAST BREAKS
THROUGH AT MORE THAN FOUR TIMES
THE SPEED OF SOUND, DESTROYING WHATEVER IS LEFT STANDING.
>> THE RESULTING SHOCK WAVE AND
THE OVERPRESSURE PRODUCED BY
THAT SHOCK WAVE COULD LEAD TO THE DESTRUCTION OF A VAST NUMBER
OF BUILDINGS IN SAN FRANCISCO.
YOU'RE PROBABLY LOOKING AT MOST
BUILDINGS BEING DESTROYED. >> Narrator: GLASS WINDOWS
SHATTER ALL OVER THE CITY.
HIGHWAY TRUSS BRIDGES COLLAPSE.
CARS AND TRUCKS ON THE ROADS ARE TOSSED ABOUT BY THE HIGH-SPEED
WINDS.
[ TIRES SQUEAL ]
AND NOW, THIS LANDSCAPE OF UTTER DESTRUCTION IS ABOUT TO BE
WASHED OVER.
THE COMET'S IMPACT HAS GENERATED
A MASSIVE MEGA TSUNAMI JUST 100 MILES OFFSHORE.
BY THE TIME IT HITS THE COAST,
THE ENORMOUS WAVE SWAMPS THE
GOLDEN GATE BRIDGE, CRASHING INTO THE BAY AND FLOODING THE
CITY.
IT ALSO TRAVELS WEST TOWARD
HAWAII AT MORE THAN 500 MILES PER HOUR. >> MORE THAN LIKELY, IF THIS
HAPPENED IN TODAY'S WORLD, MOST
OF THE CITIES ALONG THE OCEAN
WOULD BE WIPED OUT. >> Narrator: THE CITY OF
SAN FRANCISCO HAS BEEN
ANNIHILATED.
THE COMET'S IMPACT HAS SENT A PLUME OF WATER VAPOR AND SOLID
PARTICLES INTO THE AIR,
INJECTING THEM INTO THE
STRATOSPHERE MORE THAN 9 MILES HIGH.
THOUSANDS OF MILES AWAY, FIRES
FROM IMPACT FRAGMENTS AND
TORRENTIAL RAINS RAVAGE LANDS IN SOUTH AMERICA, CANADA, AND
EASTERN ASIA.
VALLEYS AND LOWLANDS FLOOD,
DECIMATING COMMUNITIES AND DESTROYING ENTIRE REGIONS.
THE IMMENSE AMOUNT OF WATER AND
HEAT INJECTED INTO THE
ATMOSPHERE CREATES STORMS OF BIBLICAL PROPORTIONS.
>> YOU COULD GET THE FORMATION
OF A SUPER HURRICANE. A SUPER HURRICANE, YOU CAN
IMAGINE, IS LIKE A CATEGORY 5
LIKE KATRINA, BUT 100 TIMES
WORSE AND MAYBE THREE TIMES BIGGER THAN KATRINA.
ONCE THAT HITS A REGION, IT
WOULD INDUCE SO MUCH RAIN, YOU
COULD GET A 1-IN-A-10,000, 1-IN-A-100,000-YEAR FLOOD.
>> Narrator: BUT THE MAYHEM IS
NOT OVER YET.
>> AS THE PLUME SPREADS ACROSS THE GLOBE, YOU WOULD GET FURTHER
COOLING.
THIS COULD INDUCE, IN SOME
SITUATIONS, EARTH GOING INTO A MINI-ICE AGE.
AND THAT WOULD PROBABLY BE THE
WORST-CASE SCENARIO IN TERMS OF
LONG-TERM CLIMATE EFFECTS IS A MINI-ICE AGE.
>> Narrator: IT WOULD TAKE
DECADES, IF NOT CENTURIES, FOR
THE PLANET TO RECOVER FROM THE CATASTROPHIC ENVIRONMENTAL
CONSEQUENCES OF THE IMPACT.
AS WE DID 4,800 YEARS AGO,
HUMANKIND WOULD LIKELY SURVIVE THIS GLOBAL DISASTER, BUT THE
WORLD WOULD NEVER BE THE SAME.
